Embodiments described herein relate generally to compositions that include diquaternary ammonium salts, and in particular to compositions that include a boronic acid based synthetic redox-active receptor that can electrochemically sense a target analyte in a sample solution.
Electrochemical sensors are defined as sensors that employ an electronic parameter, for example, current, voltage, capacitance, impedance, or any other electronic parameter to measure the concentration of a target analyte, for example, a chemical, a biochemical, or a biological analyte. Among these electrochemical sensors, amperometric electrochemical sensors (i.e., current measuring sensors) are most common. Amperometric electrochemical sensors can include a working electrode, a reference electrode and optionally, a counter electrode, which can be electronically coupled via an electrical circuit, for example, a potentiostat. The working electrode is biased at a predetermined positive (i.e., oxidation) or a predetermined negative (i.e., reduction) voltage, capable of oxidizing or reducing the target analyte, respectively. The redox reaction produces a current that is measured and compared with calibration plots to determine the concentration of the target analyte.
Known amperometric electrochemical sensors are also used as biosensors for sensing non-electroactive target analytes, for example, a biomolecule such as glucose. Such known amperometric electrochemical sensors can include a biosensing molecule such as, for example, an enzyme or a synthetic biocatalyst immobilized on the surface of the working electrode. The biosensing molecule can catalytically decompose the non-electroactive biomolecule to yield an electroactive molecule and a by-product. For example, glucose oxidase decomposes glucose to yield gluconic acid, which is non-electroactive, and hydrogen peroxide which is electroactive. The electroactive hydrogen peroxide is oxidized or reduced on the surface of the working electrode to produce a current which is measured and is correlated to the concentration of the target analyte.
Electrochemical biosensors that include conventional biosensing molecules however, suffer from numerous drawbacks. The conventional biosensing molecules, for example, enzymes, can decompose or degrade over a period of time, or when exposed to non-physiological conditions leading to degradation of the sensitivity and resolution provided by the biosensor. Conventional enzymatic-based biosensors create by-products making them susceptible to biofouling, which can reduce the diffusion of the target analyte to the biosensing molecule and/or the working electrode and degrade the electrochemical signal. Furthermore, conventional biosensing molecules consume the target analyte during the redox reaction. This can make it difficult to sense very small concentrations of the target analyte and thereby negatively impact the limit of the detection of conventional biosensors.
Thus, it is an enduring goal of electrochemical sensing systems to develop new electrochemical sensors and biosensing molecules for in vitro and in vivo measurement that can provide a higher signal to noise ratio, longer life, and do not consume the target analyte.